1. Field of the Invention
The present invention relates to aqueous dispersions of film-forming polymers prepared from ethylenically unsaturated monomers, and, more especially, to latices of acrylic or vinyl polymers containing a polyoxyalkyleneamine which includes, per molecule, at least one primary and/or secondary amine functional group.
This invention also relates to aqueous coating compositions comprising such dispersions.
2. Description of the Prior Art
Aqueous dispersions of addition polymers prepared from ethylenically unsaturated monomers are commonly employed as binders for fillers and pigments sought to be fixed or secured onto a substrate for various applications such as paints, adhesives, sealing and impermeability coatings, paper coating and the like.
For these applications, the effectiveness of the dispersion in forming a resistant film after a surface is coated depends on the glass transition temperature Tg of the dispersed polymer and on the minimum film-formation temperature MFFT of the dispersion, which determines the ability of the particles to coalesce.
It is generally desirable that the MFFT should be lower than room temperature and as low as possible. However, it is generally accepted that so-called "soft" resins of low Tg produce coatings whose resistance to wear and to soiling is less than that of the so-called "hard" resins.
A traditional technique for lowering the MFFT of a relatively hard polymer entails adding an inert plasticizer of the phthalate or polyalkylene glycol type and/or a coalescing agent to the coating composition. These additives are not entirely satisfactory and, in the case of coalescing agents which are volatile materials, they present the major disadvantage of creating environmental and atmospheric pollution risks.
Another technique for providing latices which have a low MFFT from monomers forming a "hard" polymer entails incorporating into the polymer chain hydrophilic monomer recurring structural units containing hydroxyl, amine, acetate or carboxylic acid functional groups. However, the film produced often exhibits a very high water sensitivity and a poor abrasion resistance, especially in a wet medium.